Exploiting the time of arrival of Cherenkov photons at the 28 m H.E.S.S. telescope for background rejection: Methods and performance

TL;DR

This paper introduces new timing-based methods for background rejection in the H.E.S.S. CT5 telescope, leveraging Cherenkov photon arrival times to improve gamma-ray detection at low energies.

Contribution

It presents novel techniques utilizing the timing information of Cherenkov photons for enhanced background rejection in gamma-ray astronomy.

Findings

Timing-based methods improve background rejection efficiency.

Enhanced sensitivity at lower energy thresholds.

Demonstrated performance gains over previous techniques.

Abstract

In 2012, the High Energy Stereoscopic System (H.E.S.S.) was expanded by a fifth telescope (CT5). With an effective mirror diameter of 28m, CT5 is able to detect the Cherenkov light of very faint gamma-ray air showers, thereby significantly lowering the energy threshold of this telescope compared to the other four telescopes. Extracting as much information as possible from the recorded shower image is crucial for background rejection and to reach an energy threshold of a few tens of GeV. The camera of CT5 is conceived to register the time of the charge pulse maximum with respect to the beginning of the 16 ns integration window of each pixel. This information can be utilised to improve the event reconstruction. It also helps to reduce the background contamination at low energies. We present new techniques for background rejection based on CT5 timing information and evaluate their performance.